Electric apparatus



1930. c. A. BIRCH-FIELD 1,745,974

ELECTRIC APPARATUS Filed Oct. 5, 1922 f 4O C Z [N VENTOR Chqrlas Birch-Field Patented Feb. 4, 1930 UNITED STATES PATENT OFFICE ELECTRIC APPARATUS Application filed October 5, 1922. Serial No. 592,532.

This invention relates generally to an induction arrangement and more particularly to employment of such an arrangement for tuning purposes in an apparatus receiving impulses at radio frequencies.

\Vhile the induction member and arrangement herein disclosed are particularly useful in connection with their employment as part of a radio receiving apparatus, it will be understood of course that features of my invention have a wider field of utility, and as to such features, this disclosure is intended to be only illustrative and not limitative.

It is generally the practice to employ for tuning a circuit, a continuous coil which has a sufiicient number of turns of wire to permit of cutting in and out to tune for all wave lengths within predetermined limits, and the inductance of the coil is changed for such tuning by cutting in or out more or less of the turns of wire to meet the variation in wave length.

I have found, however, that a coil of con tinuous wire of predetermined turns is most eflicient for tuning for a predetermined wave length, and that the point of final or most etficient tuning is somewhat inside of this length. Where, however, I attempted to tune for a wave length shorter than this by means of this coil of predetermined turns, I have found a lowering in the efliciency of the tuning apparatus and this I explain by the fact that such cutting out of turns produces dead ends as the result of which there is a leakage.

Where the tuning apparatus includes the employment of a primary coil and a secondary coil, which are relatively movable for tuning, it is the practice to employ one control to cut in or out more or less of the turns of one of the coils. generally the primary, and a second control to move the coils relatively of each other. In other words this part of the tuning operation generally necessitates the operation of two separate controls.

Among the more important objects of my invention therefore are; the provision of a tuning coil by which maximum tuning is attained at all times; the provision of a tuning coil in which the cutting in or out of turns thereof does not result in a lowered efiiciency; a provision of a tuning coil in which the turns of continuous wire employed is predetermined by the wave length for which maximum efficiency is desired; the provision of a tuning coil comprising separate coils; and more particularly the provision with such coil of means for connecting any desired number of coils in series to give one of a number of continuous coils varying from each other in the number of turns; the provision of a tuning coil comprising separate disconnected coils in which the turns in one of the coils is predetermined by the wave length for which maximum efiiciency is desired; the provision of a tuning apparatus including a primary and a secondary in which one of these includes a plurality of disconnected coils of varying number of turns with any predetermined one of which other coil may be inductively associated and the provision generally of a new improved and simplified tuning apparatus.

In attaining the objects referred to and gaining certain other benefits and advantages that will appear or that will be below pointed out, I have provided a construction, one embodiment whereof is illustrated in the accompanying drawings wherein:

Figure 1 is a view of one embodiment of my invention;

Figure 2 is a section on an enlarged scale through one of the switches;

Figure 3 is a top plan view of Figure 1 partly broken away;

Figure 4 is a perspective view showing the manner of successively operating the switches;

Figure 5 is a view similar to Figure 1 of a modified form of my invention;

Figure 6 is a section on line 6-6 of Figure 5;

Figure 7 is a view showing still another embodiment of my invention; and

Figure 8 shows diagrammatically a modified tuning apparatus.

Upon viewing Figure 1 it will be observed that I here show a portion of the receiiing apparatus in which 10 represents the antenna and 11 one embodiment of the tuning coil employed by me. This coil is generally made of one continuous wire and the inductance of the circuit is varied for tuning purpose by cutting in or out more or less turns of the tuning coil. This in turn produces a dead end to the continuous coil which of course will vary with the number of turns out out. have found in actual experience that the presence of this dead end generally tends to lower the efiiciency of the tuning operation. In fact I have found in actual experience that for a predetermined wave length the most efficient results by way of-tuning are attained when the continuous wire of the tuning coil is of a predetermined length, and I have further found that the point of maximum tuning is generally somewhat inside of the end of this length of coil. For example for a 360 meter wave length I have found that the most efficient tuning is attained when the primary has 36 turns and the secondary has 50 turns, the maximum tuning being attained when the primary is tapped somewhat inside of the end. For 1450 meter wave length, on the other hand, I have found that the employment .of 100 turns on the primary and 150 turns on the secondary is necessary for the attainment of the best results. If on the other hand I should use this tuning coil having 100 turns in the primary found by me to be best for 1450 meter waves length for receiving a 360 meter wave length, by cutting out turns from the coil, I find I do not attain the same good results as when I use the 36 turn primary, and this difference in result is due apparently to the resulting dead end.

For overcoming this difficulty I have devised the coil of Figure 1 which it will be observed is made up of the separate and independent short coils 15, 16, 17 and 18 the first coil 15 having one end connected to the an tenna 10 on the other end with the switch post 19. The other coils 16, 17 and 18 each have their end connected to the contact post.

19, 20, 20, 21, 21' and 22, the construction and function of which will now be set forth. It will be observed that all except the last of these posts are positioned in the pairs, 19, 19', 20, 20, 21, 21', each pair being connected to the proximate ends of adjacent coils.

Upon viewing Figures 2 and 3 in which are shown for example the construction and operation of one pair, it will be observed that the posts 19 and 19' are each arranged to receive one of the legs 23 of an L-shaped member 24 pivoted to the post 19. This L-shaped member is intended to occupy one of two positions about its pivot namely the inoperative one shown at 21 in Figure 1 and the operative shownin Figures 2 and 3 .in which the 'member 24 has been turned 90 to cause a leg 23 thereof to form a switch between the post 1919' and accordingly between the coils 15 and 16. In other words, when the switch 24 is turned to the position of Figure 2 the coils 15 and 16 become in fact one continuous coil. In the same way each pair of posts is similarly provided with a switch so that by throwing the switches in succession from left to right in Figure 1 the tuning coil can be made of any desired length.

To enable these switches 24 to be thrown in succession readily from right to left I have arranged them so that they are contacted with in succession by the switch arm 25 pivoted at 26 and arranged when turned clockwise to strike these switches in succession and operate them so as to gradually increase the turns of the coil. The arm 25 is in electrical contact with the switches and is grounded at 27 It will of course be understood that any desired means may be employed to cut out portion of the end coil, so as to attain the most eflicient tuning.

For the purpose of having the construction operate efiiciently, I preferably arranged the posts 19 etc. substantially in the arc of a circle about pivot 26, the post being cut away as shown in 28, (see Figs. 2 and 3) to receive the legs 23 of the switch 24. The switch arm 25 may if desired be cut away as shown at 29 in Figure 1. Of course it will be understood that as the switch arm 25 is moved clockwise, switches 24 are thrown in, in succession and additional turns of the coil cut in whereas when the switch is moved in the opposite dlrection, that is contra-clockwise, turns of the coil are cut out.

From the description thus far given it will be understood that by employing a suflicient number of independent coils to be connected as described and giving these coils each a predetermined length, I am enabled to attain the result of very wide tuning without at the same time having the hampering action of the dead end. In other words, I thus attain a tuning for wide limits of wave length each at maximum efficiency.

Upon viewing Figure 5 it will be observed that I here show a modified form of my invention in which the insulated arm 30 has attached to the lower surface thereof spring switches 31 arranged to connect adjacent pairs of posts connected to the ends of the coils 15, 16, 17 and 18 as do the posts 19-19' etc. in Figure 1. It will be understood that as this arm 30 is moved about the pivot 31- the switches 31 will connect in succession the pairs of posts 32, 33 for the result already set forth above. The contact member 34 is secured to the lower side of the member 30 and is arranged to ground the coil. Upon viewing Figure 6 it will be seen that the posts 33 are made shorter than 32 and one of the advantages of this is that the switch 34 will thus contact only with the post 32 which arelin direct contact with the outer end of the C01 In practical experience I have found that a great proportion of the high frequency waves received, particularly by amateurs, is at a single wave length or at approximately of the same wave length, generally 360 meters. lVith this in view I have devised the embodiment of from 3 to 7 in which the first section of 15 of the tuning coil is made of that predetermined number of turns which gives the most efficient results for that wave length. I then employ the additional coils. The coil 15 may be tapped by the switch arm as usual through the taps 40, and the coils 16, 17 and 18 may be thrown in as in Figure 1.

In Figure 8 of the drawing I show an embodiment wherein I employ any desired number of separate and distinct primaries, the four 41, 42, 43 and 44 being illustrated in the drawing, and each being of a character to operate most efiiciently with a wave of different length. For instance, the coil 43 may be of a number of turns such as will give the most efiicient tuning for a wave length of 360 meters as pointed out above, whereas coil 44 may operate similarl with a wave length of 450 meters. A doub e switch 45 is employed to selectively connect any one of these primaries with the antenna 10 and the ground 27. Each of these coils 41, 42, 43 and 44 is arranged to be tapped so as to cut turns in and out as shown at 46 in connection with the coil 41. The secondary 47 is arranged so as to be moved into inductive relation selectively with any one of these coils it being understood of course that the secondary 47 and the selected primary may be given any preferred or desired positional association for maximum inductance.

In the use of the embodiment of Figure 8 I may for instance employ a separate primary for each station or group of stations having the same wave length, and where it is desired to pick up a station at a particular point the operator will know that the coil 42 for instance is the one that operates most efficiently for that section and will actuate the switch 45 and the secondary 47 accordingly.

Having thus described my invention and illustrated its use, what I claim as new and desire to secure by Letters Patent is:

1. In an electric contact system, a movable contact member having a predetermined path of travel, a pair of contact elements arranged along said path for successive wiping encounter by said member, and means automatically operable by the latter during its movement for electrically connecting said elements, said means comprising a movable switch arm carried by one of said elements and adapted to move into a position spanning the gap between said elements.

2. In an electric contact system, a movable contact member having a predetermined path of travel, a pair of contact elements arranged along said path for successive wiping encounter by said member, and means automatically operable by the latter during its movement for electrically connecting said elements, said means comprising a movable switch arm carried by one of said elements and adapted to be encountered by the moving member for actuation by the latter into a position spanning the gap between said elements.

3. In an electric contact system, a movable contact member having a predetermined path of travel, a pair of contact elements arranged along said path for successive wiping encounter by said member, and means automatically operable by the latter during its movement for electrically connecting said elements, said means comprising a movable switch arm carried by one of said elements and adapted to move into a position spanning the gap between said elements, and said elements being provided with slots adapted to receive said arm in said spanning position.

4. In an electric contact system, a movable contact member having a predetermined path of travel, a pair of contact elements arranged along said path for successive wiping encounter by said member, and means automatically operable by the latter during its movement for electrically connecting said elements, said means comprising a movable switch arm pivoted at one end to one of said elements and adapted to swing into a position spanning the gap between said ele ments.

5. In an electric contact system, a movable contact member having a predetermined path of travel, a pair of contact elements arranged along said path for successive wiping encounter by said member, and means antomatically operable by the latter during its movement for electrically connecting said elements, said means comprising a normally upstanding switch arm pivoted to one of said elements and adapted to swing into a reclining position spanning the gap between said elements.

6. In an electric contact system, a movable contact member having a predetermined path of travel, a pair of contact elements arranged along said path for successive wiping encounter by said member, and means automatically operable by the latter during its movement for electrically connecting said elements, said means comprising a normally upstanding switch arm pivoted at one end to one of said elements and arranged to be encountered and swung by said moving member into a reclining position spanning the gap between said elements.

7. In an electric contact system, a movable contact member having a predetermined path of travel, a pair of contact elements arranged along said path for successive wiping encounter by said member, one of said elements being provided with a slot, and means automatically operable by said member during its movement for electrically vconnectmg said elements, said means comprlsmg a movable sw1tch arm adapted to move into and out of said slot and carried by the other element.

8. In an electric contact system, a movable contact member having a predetermined path of travel, a pair of contact elements arranged along said path for successive wipingencounter by said member, and means automatically operable by the latter during its movement in one direction for electrically connecting said elements and automatically operable by said member during its movement in the return direction for breaking said connection; said means comprising an L-shaped switch carried by one of said elements and adapted to move so that one arm thereof will travel between a normally upstanding position and a reclining position spanning the gap between said elements.

9. In an electric contact system, a movable contact member having a predetermined path of travel, a pair of contact elements arranged along said path for successive wiping encounter by said member, and means automatically operable by the latter during its movement in one direction for electrically connecting said elements and automatically operable by said member during its movement in the return direction for breaking said connection; said means comprising an L-shaped switch pivoted at the angle thereof to one of said elements and arranged to have one or the other arm thereof upstanding in the path of said member, one of said arms being adapted to span the gap between said elements while the other arm is upstanding.

10. In an electric contact system, a movable contact member having a predetermined path of travel, a pair of contact elements arranged along said path for successive wiping encounter by said member, and means automatically operable by the latter during its movement in one direction for electrically connecting said elements, said means comprising a movable switch arm carried by one of said elements and adapted to be encountcred and moved by said moving member into a position spanning the gap between said elements, and means automatically operable by said member during its return movement for breaking said connection, said last-named means comprising an auxiliary arm carried by said first-named arm and adapted to move into an encounterable position when said gap is spanned.

In testimony whereof I have hereunto signed my name.

CHARLES A. BIRCH-FIELD. 

